Wireless communication systems are well known in the art. Generally, such systems comprise communication stations which transmit and receive wireless communication signals between each other. Typically, base stations are provided which are capable of conducting wireless concurrent communications with a plurality of subscriber stations generically known as wireless transmit/receive units (WTRUs), which include mobile units. Generally, the term base station as used herein includes, but is not limited to, a base station, Node B, site controller, access point, or other interfacing device in a wireless environment that provides wireless access to the network with which it is associated. The term WTRU as used herein includes, but is not limited to, a user equipment, mobile station, fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wireless environment.
WTRUs include personal communication devices, such as phones, video phones, and Internet ready phones that have network connections. In addition, WTRUs include portable personal computing devices, such as PDAs and notebook computers, with wireless modems that have similar network capabilities.
WTRUs that are portable or can otherwise change location are referred to as mobile units. For mobile units, preserving battery life is generally an important consideration in designing both the mobile unit and communication networks in which it operates. There are several ways to achieve the goal of reduced power consumption in a mobile unit. For example, an increase in the number of connecting base stations within a geographic region can translate into decreased power needed for mobile unit communications.
FIG. 1a illustrates a mobile unit 104 in a wireless local area network (WLAN) 106 where a base station 102 is located at the center of the WLAN 106. As the mobile unit 104 travels away from the base station 102, the WTRU 104 and the base station 102 must increase power to ensure the same quality of service (QoS) in their wireless communication.
FIG. 1b illustrates a WLAN 112, a mobile unit 107 and nine base stations 101, 103, 105, 109, 111, 113, 115, and 117. The dense concentration of base stations reduces the distance from the mobile unit 107 to each base station. This allows the mobile units and base stations to use less transmitting power, because of the shorter distances. Such dense concentration of base stations reduces power requirements due to transmission distance, but at a cost of increased interference. The increase in interference may require the mobile units and base stations to increase transmitting power, thereby nullifying the power conservation and attendant battery life preservation.
A system can reduce interference by determining the location of each mobile unit and focusing a base station's antenna beam pattern at each mobile unit's direction. Focusing an antenna's beam pattern is also known as beam forming.
FIGS. 2a–c illustrate antenna radiation patterns in a system using beam forming such as disclosed in U.S. patent application Ser. No. 10/305,595 owned by the assignee of the present application. FIG. 2a illustrates a base station 10 with an antenna pattern 12 that concentrates radio frequency energy to and from a mobile unit UE1 based on the mobile unit's relative location.
Beam forming can be selectively utilized in the servicing of multiple wireless concurrent communications with multiple beams or a single beam which is controlled based upon factors such as location and relative interference. FIGS. 2b and 2c illustrate two different scenarios of base station 10 concentrating radio frequency energy to and from mobile units UE2 and UE3 based on different mobile unit relative locations.
To utilize beam forming, the location of the mobile unit must first be determined. Location determination can be achieved by any of a variety of known methods. For example, the mobile unit can determine its own location using a built-in global positioning system (GPS) receiver and report its location to the network. A network can also determine the location of a mobile unit using AOA (Angle of Arrival), TDOA (Time Difference of Arrival), or Doppler techniques. A hybrid method can be used where a network assists a mobile unit to determine its own location. Generally, each method produces an estimate of the relative mobile unit location with an associated margin of estimation error.
There are many ways for service providers to offer and control network access. For example, a popular wireless local area network protocol with one or more WLAN access points may be built on the IEEE 802.11b standard. In some such networks, selected WLAN service may be provided in relatively small, well defined geographic areas known as “hot spots.” These areas allow users the ability to go “on-line” with their mobile units and access a wireless network.
“Hot Spot” WLAN communication systems can advantageously be deployed in many locations, such as airports, coffee shops, and libraries. Access to these networks is typically achieved through a user authentication procedure. As the IEEE 802 families of standards are always evolving, such procedures are not yet fully standardized in the WLAN technology area.
Applicants have recognized a problem with “hot spot” communications in that a user may have trouble locating where the hot spot communication areas are, more particularly where the user should be physically located to obtain the best QoS within the WLAN.